Case Study

Mineral Processing - Backfill

Project Description

In this mineral processing operation, volumes of fine mud must be disposed of after all the valuable mineral material has been extracted. Disposal of the waste slurry underground reduces the quantity that is present in the tailings pond and is also useful for reducing the stresses in the walls of the underground mine. One mine had a deep ore body that extended nearly vertically.

The mining plan was to start near the bottom of the ore body and fill the mined-out voids with hydraulic backfill consisting of a mixture of slurry, sand and cement. The client had practiced hydraulic backfill at their other operations. However, this operation required backfill to be mixed and poured on a nearly continuous basis.

MixPro® Challenge

MixPro® was asked to design the agitators which would fully suspend the fast-settling sand slurry, be highly reliable and most cost effective. This would be their largest backfill plant system and its operation would be critical to the mining plan.

The density of the sand-slurry was to be as high as a centrifugal pump could handle in order to reduce the volume of water that needed be returned to the surface. This meant the slurry density and viscosity would be higher than any other operating back-fill system.

We worked very closely with the customer's engineering firm to ensure its success.

Recommended Solution

We visited the customer's existing successful installations where sand backfill was maintained in suspension with old agitators supplied by other companies. The speed reducer had been replaced several years earlier by Sumitomo and was working very well. Sumitomo had also supplied the same reducer and ratio for several conveyor drives.

After obtaining a large sample of the fast settling de-slimed backfill slurry, we conducted a long test program to determine the agitation requirements for the large backfill storage tanks. It was determined that the exact same Sumitomo speed reducer, (PVD9105R3-L-RL-40 & 38.853:1) that was operating at the customer's other locations could be used for the new larger backfill operation. This could be achieved by lowering the operating speed with a 6-pole motor. This provided the customer with both commonality of replacement parts and a reducer supplier that was attentive to their needs.

Project Success

The large backfill storage agitators have been operating problem free. We worked very closely with the customer's engineering firm to ensure its success.